Abstract
In the past, efficiency indices have been proposed as a means of expressing child progress from developmental data. In the present article, a variation of a previous index is proposed and examples are shown depicting the utility of the proposed variation. The proposed variation, the Proportional Change Index (PCI), is a numerical statement of the relationship between children's rate of development during intervention with the rate of development at the time intervention began. It allows comparisons of program efficiency across children with varying severity levels of handicapping conditions, different chronological ages, and developmental abilities.